Drayton MiTime 720R programmer instalation help

11 Apr 2015
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United Kingdom
Can anybody give me help and advice on how to install a Drayton 720R 2 channel rf pragrammer to a Baxi combi 105 HE boiler?
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What do you want to know ?

Why two channel on a combi so how is boiler and installation set up?
Step 1 look at the instruction for the Baxi Next look at instructions for Drayton and you will see the Baxi only has only one set of cables for an external device. If any timers are required one would normally have them built into the boiler not independent.

You can fit a timer but it would only require a single timer not a double one. Even though no earth is required one will still be taken to the Drayton just in case needed in the future so normally would be triple and earth cable. So all but the L go to Drayton.

At Drayton N to N and 1 to L and 2 to 4 that is it. However it does seem rather pointless. Using something like a Horstmann DRT2 Programmable Digital Room Thermostat (27468) wired or Horstmann HRFS1 Programmable Room Thermostat (93829) wireless it not only does the time but also does the temperature it seems to me you have the wrong product match.

I think the whole idea of room thermostats is some what dated as in the main with any condensation boiler we use thermostatic radiator valves and as a result controlling temperature in any one room does not really work.

I am not sure what an "anticipator" is but the instructions say you must use one when a thermostat is used.

I would be interested to find out what the "anticipator" is? From what I am lead to believe boilers today have anti-cycle software and are designed to monitor when heat is required and to auto shut down when all TRV have closed re-trying after a time which alters according to the results after each re-try.

To add external electrical controls may upset this software I am guessing the "anticipator" is to stop the software being messed up with external electrical switching? I am lead to believe you can get electrical heads for the TRV which include timers so each room has a time not the boiler as a whole. I have been considering fitting these for my mother but a yet not quite sure what fits what with different makes of TRV.

Since hot water is instant there is not need for any timer on hot water.
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Thanks for that i wasnt sure wheather i took a live and neutral from boiler supply to power the programmer and switched the CH on/off turning the volts around via a relay. But i see now that i use the volts from the existing time clock circuit to power the programmer. Is there a constant 240V on term1 on boiler?. I will get fluke out and have a check. Thanks once again for advice
Diagram says yes there is 230 volt. Sorry I see the link could not be activated due to the enlarge feature of the picture. Modified now so you can click on Baxi.

Page 23 is the question. What is an anticipator thermostat? after reading is seems to be the small heated fitted in mechanical thermostats to reduce the difference between switch on and switch off.

With old thermostats if the neutral was not wired in this feature would not work. It had a duel role it reduced the differential and also compensated for the heat held in radiators after they switch off.

I am surprised even talked about as with a condensate boiler it does not simply turn off and on but varies flame hight. So the thermostat only stops boiler cycling during the summer.
Hi every one.

Its great tread. Its very helpful.
I got similar problem. I wich to svap poterton controler ep2002 with the same drayton one with wireles termostat. Some body on the forum says is would be work. Just wondering how is about the wiring from one to other one.
I have used many thermostats and timers, in the old days boilers simply turned on or off, and they worked of sorts, but today as already said the condensation part of the boiler needs the return water temperature to be below a set figure so they no longer turn on and off but use the return water temperature to adjust flame size so in theory as each one of the TRV (thermostatic radiator valve) turns off the system adjusts to suit.

The problem is the boiler can be too clever and unless the lock shield valves and TRV's are set correct the whole system can fall over.

There is a system called Evohome which is designed to work with special TRV's which monitor the temperature and time for every room so although the boiler is central each room is independently controlled, however it is expensive.

So what we try to do is use cheaper options to get what we want, at least I have. However they tend to fight each other for control, so it takes a lot of tweaking to get it to run well.

With a system left running 24/7 the TRV will look after its self. The problem is after the system is turned off. So what is all important is the lock shield valve. If they are left wide open then what happens is all the hot water goes to one radiator, as the room warms up, the radiator switches off and it all goes to next radiator, and so room by room the house is warmed up again. The returning hot water switches the boiler down to minimum setting and the house holder thinks the boiler is not big enough. Reducing the flow in each radiator means they all get hot water together and no hot water returns to boiler until all radiators are hot. Once the bypass valve opens as every TRV closes then the boiler will shut down, it will shut down for a time which varies, and then it tries firing up and testing the return water temperature, if still high it increase the time before next try, if not it decreases the time before next try, this is the anti-cycle software working.

However if the supply to the radiator is cut by a timer rather than temperature then the boiler will think the house is hot enough and increase the re-try time to a much too long of a time, so once the timer switches on, there is no hot water being pumped around, so there is a delay before the boiler starts.

This delay is compounded by the thermostat delay as well, the result is you come home to a cold house.

When I wrote the first reply I was unaware of the thermostat delay. I have a hard wired thermostat and timer at home, so at 6 am the temperature set changes from 14°C to 20°C and boiler starts straight away. However mothers house has a wireless thermostat and from time set it takes 15 minutes some times before the two have shaken hands and the boiler has started.

Today for some unknown reason my mother sat in her wheel chair at the back door with it wide open, the house temperature went down, and 1/2 hour latter the boiler cut in to re-heat the house, lucky I have a stand alone fire I could use while I waited for the thermostat to talk to the base unit. But there is no data with the thermostat timers to tell you what delay they have.

So unless you can afford EvoHome then best is to use timer built into boiler, and not use any exterior add on devices. Learn from my error.

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